Structures are already known that comprise:
two components made of composite material, each having an outside face and an inside face and disposed in such a manner that the inside face of the first of said components overlies, at least in part, the outside face of the second of said components, the overlaid portions of said components including pairs of holes in alignment;
screws with countersunk heads, each screw passing through one of said pairs of holes in alignment so that its head is received in countersinking provided in the outside face of said first component; and
nuts suitable for co-operating with respective ones of said screws and for bearing against the inside face of said second component to press the countersunk head of the corresponding screw into said countersinking.
When such a structure is subjected to the action of lightning, the discharge current propagates via said screws and causes arcs to appear between said nuts and the inside face of said second component. Such arcs may destroy the structure, particularly if the structure constitutes a fuel tank, in which case the arcs may ignite the fuel.
To remedy this drawback, documents U.S. Pat. No. 4,891,732 and GB-A-2 212 580 propose insulating said first and second components electrically from each other and dissipating the discharge current passing through them by facilitating the flow of said discharge current firstly between the screw heads and the first component, and secondly between the ends of said screws opposite to their heads and said second component. This results in a structure for said nuts and/or for their disposition relative to said second component that is complex.
An object of the present invention is to remedy this drawback of complexity and to make it possible to enable the structure to withstand lightning strikes while using standard nuts only.